A chemosorptive cylindrical denuder designed for personal exposure measurements of isocyanates–evaluation on generated aerosols of 4,4′-methylenediphenyl diisocyanate

Abstract

A denuder/filter system constructed for solvent-free personal exposure measurements was evaluated for separation of vapour and particulate 4,4′-methylenediphenyl diisocyanate (4,4′-MDI) generated from heated PUR-foam. The two different phases were collected in the denuder and on the filter, respectively, by chemosorption on a polydimethylsiloxane (SE-30)–dibutylamine (DBA) stationary phase. Both repeatability and the total mass concentration of 4,4′-MDI were similar to that obtained from the reference method, in this case an impinger/filter system. The penetration of particles through the denuder at 300 ml min⁻¹ was nearly 100% in the particle size range 25 to 700 nm, which fits well with the Gormley–Kennedy equation. Denuder/filter sampling of the 4,4′-MDI aerosol at 500 ml min⁻¹ yielded a phase distribution that was in accordance with the results from the reference method. The method limit of detection was 6 ng m⁻³ and 4 ng m⁻³ for the denuder and filter, respectively, when using an air sampling flow rate of 300 ml min⁻¹ and a sampling period of 15 min. This is well below the Swedish occupational exposure limit (OEL) of 50 and 100 μg m⁻³ for an 8-hour working day and a 5-min period, respectively.